Ladder

ABSTRACT

A ladder comprises two stringers, a plurality of rungs and fastening elements for fastening said ladder to structure, said fastening elements and said rungs being provided, at their ends with external toothing and the stringers carrying a plurality of shiftable and clampable connecting elements some of which are provided with a blind bores for receiving ends of said rungs and others of which are provided with bores for receiving ends of said fastening elements.

United States Eatent [191 1 3,786,899 Zenhausern [451 Jan. 22, 1974 LADDER 3,443,351 5/1969 Kuniazawa ..'52/704 1 Inventor: Heinrich 32221332 351323 2?;;;;;i:::::...::: .11.???5352 Birmensdorferstrasse I34, Urdorf, Switzerland [22] Filed: Aug. 24, 1971 [21] Appl. No.: 174,441

[30] Foreign Application Priority Data Aug. 27, I970 Switzerland l2964/70 [52] U.S. Cl. 182/93, 182/228 [51] Int. Cl. E06c 9/02, E060 7/08 [58] Field of Search. 182/46, 93, 229, 52, 194, 228; 52/704 [56] References Cited UNITED STATES PATENTS 267,031 11/1882 Spelman 182/52 Primary ExaminerReinaldo P. Machado Attorney, Agent, or FirmStepno, Schwaab & Linn 5 7 ABSTRACT A ladder comprises two stringers, a plurality of rungs and fastening elements for fastening said ladder to structure, said fastening elements and said rungs being provided, at their ends with external toothing and the stringers carrying a plurality of shiftable and clampable connecting elements some of which are provided with a blind bores for receiving ends of said rungs and others of which are provided with bores for receiving ends of said fastening elements.

1 Claim, 3 Drawing Figures PATENTED JAN 2 2 I974 sum 1 OF 3 PATENTED JAN 2 21974 SHEET 2 UF 3 PATENTEDJAHZZW 3; 786,899

sum 3 or. 3.

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LADDER FIELD OF THE INVENTION This invention relates to ladders which can be attached to structures to facilitate climbing thereon.

DISCUSSION OF PRIOR ART In sewer shafts, water reservoirs or clarification plants, on house walls, industrial chimneys or similar objects, an arrangement is generally known which makes possible the negotiating of the same. Thus in sewage plants there are climbing irons which are cemented into the wall of the shaft and form a ladder or steps via which one can easily climb down into the shaft.

Since the conventional mounting of these climbing irons by cementing-in is not only complicated and timeconsuming but also expensive, it has already been proposed to mount such climbing irons on brackets attached to plugs sunk in the shaft wall. By this means the great danger of oxidation and rusting of the cementedin ends of the climbing irons can be reduced, particularly if the brackets are produced from a material which has a great resistance to moisture, corrosive gases and chemicals.

However, it is often more expedient, instead of mounting individual climbing irons or elements on the wall, to mount a complete ladder. A ladder possesses a great inherent stability and the number of anchoring points is reduced quite substantially. However, a disadvantage when using already formed ladders arises in that the points of attachment of the ladder are fixed and so a highly precise mounting of anchors on the shaft wall is necessary. Moreover, for each shaft, a ladder adapted in its size to the shaft must be used, which means that a large stock must be kept by a supplier.

OBJECT OF THE INVENTION It is an object of the present invention to provide a ladder which does not have the above disadvantages and can be used in all types and sizes of shafts and on walls, chimneys and other structures.

Accordingly the invention provides a ladder, for attachment to a structure, comprising a plurality of rungs, two stringers and fastening elements, said rungs and said fastening elements being provided at their ends with external toothing and said stringers carrying a number of shiftable and clampable connecting elements some of which elements are provided with at least one blind bore for receiving a free end of one of said rungs and others of which are provided with bores for receiving respective one ends of said fastening elements.

The ladder of the invention can be assembled in situ and be made up to a desired size and configuration as desired. It is stable and resistant to corrosion. The stability of the ladder of the invention can be enhanced by the external toothing being formed by a number of circular barb-like ribs, which ribs have an inclined flank directed towards the end of the rungs or stringers and a flank extending perpendicularly to the axis of the rungs or stringers. Furthermore, it is advantageous if the rungs, stringers and fastening elements are in the form of steel tubes provided with a coating of polyethylene or aluminium. Alternatively the rungs, fastening elements or stringers can be made from aluminium tube provided for reinforcement, with internal radially directed webs or cross pieces which extend over their entire length.

In a preferred embodiment of ladder conforming to the invention the rungs and/or fastening elements can carry, on their ends, a respective pressed-in plastic pins or tenons provided with the external toothing. The external toothing can be formed in the polyethylene coating or in an aluminium tube itself.

DESCRIPTION OF A PREFERRED EMBODIMENT The invention will be described further, by way of example, with reference to the accompanying drawings, wherein FIG. 1 is a perspective view of a preferred embodiment of ladder conforming to the invention and mounted in a shaft;

FIG. 2 is a cross-section through a junction of a rung with a stringer of the ladder of FIG. 1 showing a connecting element thereof; and

FIG. 3 illustrates, partly in section, a fastening element of the ladder of FIG. 1.

The ladder of FIG. 1 comprises a number of rungs 1, two stringers 2 and four fastening elements 3. Provided in the structure of shaft 4, for mounting the ladder are a number of sleeve-like anchoring elements 5, each of which has a slightly frusto-conically tapered bore which corresponds, in diameter to the fastening elements 3. These elements 5 can be cast integral, for example during construction of the shaft in accordance with a specific arrangement, in which case not-needed sleeves are sealed with a stopper 6 or the sleeves can be subsequently inserted into holes formed in the shaft. In this latter case the sleeves can be provided with barb-like external ribs 7, as shown in'FIG. 3.

Those ends of the elements 3 which are inserted into the bores of the sleeves 5 are provided with barb-like ribs 8 which can be formed directly in the polyethylene or aluminium coating surrounding the fastening elements 3, as shown in FIG. 3, or a pin or tenon 9 can be provided which is pressed into the end of each fastening element 3, as is shown in FIG. 1.

The fastening elements 3 are fastened by means of connecting elements 10 to the stringers 2. Similarly designed connecting elements 11 connect the rungs 1 to the stringers 2, and one embodiment of connecting element 11 is represented in section in FIG. 2. It possesses a blind bore 12 which is slightly frusto-conically tapered. The bore 12 serves for receiving the one end of a rung 1. Each of the rungs 1 is provided, at its ends, with barb-like toothing in the form of ribs 13 which ensure a secure fit in the bore 12 of the connecting element 11. It is advantageous to seal the hollow end of the rungs 1 in an air-tight and damp-proof manner with a stopper 14. A corresponding sealing, which is not represented in more detail in the drawing, is undertaken at the ends of the fastening elements 3 and of the stringer 2. As is further clearly evident from FIG. 2, the connecting elements 11 possess a continuous bore 15, which is likewise slightly frusto-conically tapered and which has a somewhat greater diameter than the stringer 2. They can thus be displaced, together with the rungs 1, along the stringers 2 to any desired position and can be fastened by means of frusto-conically shaped sleeves such as the sleeve 16 which is pressed into the bore 15. If required, the outer surface of the sleeve 16 and/or the inner surface of the conical bore 15 can additionally be provided with barb-like toothing in the form f ribs 17. if desired, connecting element 11 may have a clamp-like connector structure, as shown with respect to element 10, for cooperation with stringers 2.

It has been proved to be very favourable to produce the connecting elements 11, as well as the stoppers 16, from a resistant, but nevertheless somewhat elastic, plastics material such as nylon.

If, moreover, steel tube provided with a polyethylene coating, is used for the rungs l, for the stringers 2 and for the fastening elements 3, an excellent and permanent insulation of the entire climbing arrangement in relation to the brickwork can be achieved.

In FIG. 3, a second embodiment of a connecting element which may be used in place of connector or 1 1 is illustrated in which the ends of rungs 1 and fastening elements 3 are provided with a plurality of independent, circular barb-like flanges adapted to directly cooperate with the grooved frusto-conical bore of the connector.

With the ladder of the invention the possibility is provided of guaranteeing the negotiability of structures provided with it for years to come with great safety. There exists very little danger of breakage as a result of corrosive attacks, and also tearing-out or breakingaway of the fastening elements from the structure is highly unlikely. However, the possibility exists of dismantling the ladder undamaged, by means of suitable tools. Upon the erection of the ladder arrangement, no working with hammer and chisel nor any plaster work whatever is necessary, so that the erection can be effected in the shortest time by unskilled labour.

The ladder can have an upper extension for resting on part of a structure above it for extra support.

The invention is not limited to the precise details of the foregoing embodiment and variations may be made thereto within the scope of the following claims.

I claim:

1. A ladder for attachment to a structure comprising a pair of parallel, spaced continuous stringers, each formed of a single, unbroken tubular element;

a plurality of generally tubular rungs;

first means connecting the ends of each of said rungs to said stringers, each of said first connecting means secured in spaced relation about one of said tubular stringers and defining a frusto-conical bore having a plurality of independent circular grooves each having a first flank perpendicular to the axis of said groove and a second flank inclined thereto;

the ends of each of said rungs having a plurality of independent, circular barb-like ribs formed thereon for establishing a permanent interconnection between said rungs and said stringers upon direct insertion of said rung ends into said first connecting means;

anchor means adapted to be permanently attached to the structure and defining a frusto-conical bore having a plurality of independent circular grooves each having a first flank perpendicular to the axis of said groove and a second flank inclined thereto;

a plurality of generally tubular fastening elements;

and

second means connecting one end of each of said fastening elements to one of said stringers, each of said connecting means secured in spaced relation about one of said tubular stringers and defining a frusto-conical bore having a plurality of independent circular grooves each having a first flank perpendicular to the axis of said groove and a second flank inclined thereto;

the ends of each of said fastening elements having a plurality of independent, circular barb-like ribs formed thereon for establishing a permanent interconnection between said stringers and the structure upon direct insertion of said fastener element ends into said second connecting means and said anchor means. 

1. A ladder for attachment to a structure comprising a pair of parallel, spaced continuous stringers, each formed of a single, unbroken tubular element; a plurality of generally tubular rungs; first means connecting the ends of each of said rungs to said stringers, each of said first connecting means secured in spaced relation about one of said tubular stringers and defining a frusto-conical bore having a plurality of independent circular grooves each having a first flank perpendicular to the axis of said groove and a second flank inclined thereto; the ends of each of said rungs having a plurality of independent, circular barb-like ribs formed thereon for establishing a permanent interconnection between said rungs and said stringers upon direct insertion of said rung ends into said first connecting means; anchor means adapted to be permanently attached to the structure and defining a frusto-conical bore having a plurality of independent circular grooves each having a first flank perpendicular to the axis of said groove and a second flank inclined thereto; a plurality of generally tubular fastening elements; and second means connecting one end of each of said fastening elements to one of said stringers, each of said connecting means secured in spaced relation about one of said tubular stringers and defining a frusto-conical bore having a plurality of independent circular grooves each having a first flank perpendicular to the axis of said groove and a second flank inclined thereto; the ends of each of said fastening elements having a plurality of independent, circular barb-like ribs formed thereon for establishing a permanent interconnection between said stringers and the structure upon direct insertion of said fastener element ends into said second connecting means and said anchor means. 